Seals seated in machined grooves have long been used to affect a sealing surface within mechanical apparatus. Typical of such seals are quad ring seals, spring loaded lip seals or even o-rings that seal an annulus defined by concentric cylindrical surfaces. In such an arrangement, the seal is typically seated in a groove machined within either or both of the annular surfaces, and the seal forms a complete seal within the annulus.
Often, the two surfaces defining the space sealed by the seals move relative to each other, typically by rotation such as a rotating shaft displaced within a stationary cylinder. Over time, the surfaces may wear where they are in contact with the seal because of friction caused by the relative movement. Such wear can cause leakage along the surfaces in contact with the seal. Such wear and resulting leakage is expensive to repair, typically requiring the apparatus in question to be removed from service and the part bearing the worn surface to be completely replaced or resurfaced, processes which are labor intensive.
The two surfaces defining the space sealed by the seals may become polished by extended rotation, causing a smoother surface that may be incompatible with a particular seal. For example, quad ring seals are typically compatible with a surface of finish 24 to 32 Ra, and spring loaded lip seals are compatible with a surface finish of 14 to 18 Ra. The contact of a seal against a shaft will over time increase smoothness beyond the range of the seal, resulting in leakage. To merely replace the seal is ineffective because the smoothness of the worn shaft is not compatible with the new seal.